When transmitting data via an optical transmission medium such as a fibre the transmitted optical signal can be affected by a non-linear effects and phase noise with increasing length of the fibre and with increasing data transmission speed. Especially for long haul data transmission distances in excess of 1500 km and data transmission rates of more than 100 GBit/Sec these effects can be noticed.
Accordingly, it is an object of the present invention to provide an apparatus and a method which allow to increase a data transmission rate of data which can be transported in a given optical bandwidth.